1. Field of the Invention
The present invention relates to a liquid crystal display apparatus of a simple matrix driving type, which has a plurality of row electrodes (scanning lines) and column electrodes (signal lines) arranged in matrix form, and drives all of column electrodes during driving one row electrode.
2. Related Background Art
In the liquid crystal display (LCD) apparatus of the simple matrix driving type, there is a system scanning the row electrodes arranged to a horizontal direction of a display screen line by line. On the LCD screen, only one line is lighten in a moment. However, because lightening is repeatedly carried out, an eye of human is perceived so that all the screen is lightening.
On the other hand, when the LCD screen becomes large and the number of the scanning lines increases, if each row electrode is not scanned at high speed, a flicker is likely visible. In order to reduce the flicker, it is necessary to set the number of scanning frame to more than 25 times per one minute. One frame time, that is, a lightening time for one line is set by the number of scanning frames per one minute. The more the number of the scanning lines is, the shorter the lightening time is. The shorter the lightening time for one line is, the lower the ratio of ON/OFF of the liquid crystal, that is, a contrast ratio becomes; as a result, the more the screen image is blurred.
By improvement of the liquid crystal material, it is possible to compensate deterioration of the contrast. However, undesirable problems such as shadowing and waving occurs, thereby deteriorating display quality. The shadowing designates a phenomenon that shadow emerges at non-lightening points, as shown in FIG. 1. In order to reduce the shadowing, it is general to detect turning point of the ON/OFF of the liquid crystal and to apply a supplement voltage at the points. However, because a circuit for detecting the turning points of the ON/OFF and a circuit for applying the supplement voltage has to be added, the cost is up and mounting area becomes necessary too much.
Next, the waving will be explained. The liquid crystal has a characteristic that its properties deteriorate when the voltage is applied only to one direction. Therefore, ordinarily, the polarity of the voltage applied to the liquid crystal is periodically switched, and the voltage applied to the liquid crystal is controlled so as to become plus minus zero. As a specific method of the polarity inversion, there are a frame inversion that the polarity inverts at each frame (each screen), and a dot inversion that the polarity inverts at each dot.
For example, in the case of the line inversion, if the polarity inversion is carried out at every submultiple pieces of all the horizontal lines, the polarity is inverted by the same line at each frame. As a result, the line showing change-over of the polarity is perceived.
On the other hand, in the case of the frame inversion, as a property of CMOS transistor constituting the driving circuit, penetrating current flows. Therefore, the driving voltage goes down and the contrast changes undesirably.
Because of this, in the liquid crystal display apparatus of simple matrix driving type, the polarity is switched at every prime factor pieces of lines, for example, 13 or 17 pieces. When the polarity is switched at every the prime factor pieces of lines, a least common for the number of all lines becomes large, and the location that the polarity of the driving voltage switches changes at each frame. As a result, the line showing change-over of the polarity is not perceived.
However, even if inverting the polarity at every prime factor pieces of lines, there is a case that the line to switch the polarity inversion is perceived so that the wave flows. In order to reduce such a waving, it is necessary to provide the horizontal lines more than the number of the horizontal lines in the display area and to prevent the occurrence of the wave by controlling a surplus divided by a prime factor. Because of this, the scanning control is complicated and a new circuit becomes necessary.
The present invention has been developed in consideration of the above-described respects, and a object of the present invention is to provide a liquid crystal display apparatus capable of reducing the shadowing and the waving.
To attain the above-described object, according to the present invention, there is provided a liquid crystal display apparatus comprising:
a plurality of row electrodes and column electrodes arranged in matrix form;
a row electrode driving circuit for driving each of said row electrodes in random order; and
a column electrode driving circuit for driving each of said column electrodes.
According to the present invention, because each of the row electrodes is driven in random, it is possible to reduce the shadowing depending to the video data. Furthermore, because the adjacent row electrodes are not continuously scanned, the waving does not occur and the display quality is improved.
In the present invention, if pattern strings showing the scanning order of the row electrodes is stored in the storing apparatus in advance, it is possible to quickly decide the scanning order of the row electrodes and to surely drive each of the row electrodes within a prescribed time, even if there are a lot of the row electrodes.